JP2003259244A - Ground wave digital broadcasting receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To switch segments in a short period of time if the switching range of the segments is a fixed range about a ground wave digital broadcasting receiver used for receiving ground wave digital broadcasting that adopts an OFDM (orthogonal frequency division multiplexing) modulation system. <P>SOLUTION: A tuner 12 receives a segment, an FFT (fast Fourier transform) circuit 17 performs FFT processing corresponding to three segments, and the I/Q symbol data of the three segments outputted by the FFT circuit 17 are stored in FFT output buffers 18 and 19. When segments are switched between the segments stored in the FFT output buffers 18 and 19, I/Q symbol data outputted from the FFT output buffers 18 and 19 are switched without resetting a selection frequency of the tuner 12. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to OFDM (Orthog
The present invention relates to a terrestrial digital broadcasting receiver used for receiving terrestrial digital broadcasting adopting an onal Frequency Division Multiplex (orthogonal frequency division multiplex) modulation method.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram of a main part of an example of a conventional terrestrial digital broadcast receiver. In FIG. 4, reference numeral 1 is a receiving antenna, and 2 is a tuner for performing frequency conversion and channel selection of the terrestrial digital broadcasting signal received by the receiving antenna 1. As a band extracting band pass filter, a SAW having a bandwidth of 1 segment is used. It has a (Surface Acoustic Wave) filter.

Reference numeral 3 is an OFDM demodulator, 4 is an A / D conversion circuit for converting the OFDM signal output from the tuner 2 into a digital signal, and 5 is orthogonal demodulation of the OFDM signal output from the A / D conversion circuit 4. It is a quadrature demodulation circuit.

Reference numeral 6 denotes an I / Q output from the quadrature demodulation circuit 5.
It is a frequency / clock synchronizing circuit that inputs a signal and removes a narrow band frequency error within a carrier interval and a wide band frequency error in a carrier interval unit.

Reference numeral 7 is an FFT (Fast Fourier Transform) circuit for extracting a signal in an effective symbol period from the I / Q signal output from the frequency / clock synchronizing circuit 6 and performing fast Fourier transform to output I / Q symbol data. .

Reference numeral 8 is an FFT output buffer for temporarily storing the I symbol data output from the FFT circuit 7, and 9 is an FFT output buffer for temporarily storing the Q symbol data output from the FFT circuit 7.

Reference numeral 10 is a detection circuit for performing differential detection or synchronous detection on the I / Q symbol data output from the FFT output buffers 8 and 9. The error correction circuit provided in the subsequent stage of the detection circuit 10 is not shown.

FIG. 5 is a diagram for explaining a channel selection system adopted by the conventional terrestrial digital broadcast receiver shown in FIG. 4, and FIG. 5A is a 6 MHz band which is divided into 14 segments and transmitted in a concatenated manner. Of the OFDM signal.

Here, for example, in the case of selecting the segment 7, as shown in FIG. 5B, the center frequency f7 of the segment 7 is set in the tuner 2 as the selection frequency.
By doing this, the tuner 2 to the OF of the segment 7
The DM signal is output, the FFT process is performed on the segment 7 as shown in FIG. 5C, and the detection process is further performed on the segment 7 as shown in FIG. 5D.

Further, in the case of switching the channel selection to the segment 8 from the state of selecting the segment 7 in this way, as shown in FIG. 5E, the center frequency f of the segment 8 is
Set 8 as the tuning frequency in tuner 2 again. In this way, the tuner 2 outputs the OFDM signal of the segment 8, the FFT processing is performed on the segment 8 as shown in FIG. 5F, and further, as shown in FIG. 5G.
The detection process will be performed on the segment 8.

[0011]

In the conventional terrestrial digital broadcasting receiver shown in FIG. 4, when the segment to be tuned is switched, the tuning frequency of the tuner 2 is set again. Required, OFD
There is a problem that the output of the MPEG transport stream from the M demodulation device 3 is delayed.

In view of the above points, the present invention has an object to provide a terrestrial digital broadcast receiver capable of performing segment switching in a short time if the segment switching range is within a certain range. And

[0013]

A terrestrial digital broadcasting receiver of the present invention comprises a tuner capable of receiving a plurality of segments, an FFT circuit corresponding to the plurality of segments,
It has a holding circuit for holding a plurality of segments of data output from the FFT circuit.

According to the present invention, the desired segment can be selected by outputting the signal of the desired segment from the signals of the plurality of segments held by the holding circuit and performing the detection processing. That is, within the range of a plurality of segments received by the tuner, the segments can be switched without resetting the tuning frequency of the tuner.

[0015]

1 is a circuit diagram of a main part of an embodiment of the present invention. In FIG. 1, 11 is a receiving antenna, 12 is a tuner that performs frequency conversion and channel selection of the terrestrial digital broadcasting signal received by the receiving antenna 11, and has a bandwidth of 3 segments as a bandpass filter for band extraction. It has a SAW filter.

Reference numeral 13 is an OFDM demodulator, 14 is an A / D conversion circuit for converting the OFDM signal output from the tuner 12 into a digital signal, and 15 is an A / D conversion circuit 14.
It is an orthogonal demodulation circuit that orthogonally demodulates the OFDM signal output from

Reference numeral 16 denotes I output from the quadrature demodulation circuit 15.
It is a frequency / clock synchronization circuit that inputs a / Q signal and removes a narrow band frequency error within a carrier interval and a wide band frequency error in carrier interval units.

Reference numeral 17 is an FFT circuit for extracting a signal in the effective symbol period from the I / Q signal output from the frequency / clock synchronizing circuit 16 and subjecting it to fast Fourier transform to output I / Q symbol data.

Reference numeral 18 is an FFT for temporarily storing the I-segment data of three segments output from the FFT circuit 17.
Output buffer, 19 is 3 output from the FFT circuit 17
FF that temporarily stores the Q symbol data of the segment
T output buffer.

Reference numeral 20 is a detection circuit for performing differential detection or synchronous detection on the I / Q symbol data of one segment output from the FFT output buffers 18 and 19. Reference numeral 21 is the tuner 12, the FFT circuit 17 and the FFT output buffer 1.
The frequency shift control circuit controls 8 and 19. The error correction circuit provided in the subsequent stage of the detection circuit 20 is not shown.

FIG. 2 is a diagram for explaining a channel selection method adopted by an embodiment of the present invention. FIG. 2A is an OF of 6 MHz band which is divided into 14 segments and transmitted in a concatenated manner.
It represents a DM signal.

Here, for example, when selecting the segment 7, the central frequency f7 of the segment 7 is set in the tuner 12 as the selection frequency as shown in FIG. 2B. By doing so, the tuner 12 outputs the OFDM signals of the segment 6, the segment 7, and the segment 8.

In this case, the FFT circuit 17 is controlled by the frequency shift control circuit 21 to perform the FFT processing corresponding to the three segments, and as shown in FIG. 2C, the FFT for the segment 6, the segment 7, and the segment 8 are performed.
Processing is performed, and the I / Q symbol data of the segment 6, the segment 7, and the segment 8 are processed by the FFT output buffer 1
8 and 19 are stored.

Further, the frequency shift control circuit 21
The I / Q symbol data of the segment 7 is output from the FFT output buffers 18 and 19 under the control of the I / Q symbol data of the segment 7 in the detection circuit 20 as shown in FIG. 2D.
Detection processing is performed on the Q symbol data.

Further, when the user switches the channel selection to the segment 8 from the state of selecting the segment 7 in this way, the tuner 12 sets the channel selection frequency to f7, and the segment 6, segment 7 and segment 8 are selected. 2E is maintained, and the FFT circuit 17 is also maintained in the state of performing the fast Fourier transform for the segment 6, the segment 7, and the segment 8 as shown in FIG. 2E.

However, the FFT output buffers 18 and 19 are controlled by the frequency shift control circuit 21 to output the I / Q symbol data of the segment 8, and the detection circuit 20 outputs the segment 8 as shown in FIG. 2F. Differential detection or synchronous detection is performed on the I / Q symbol data of.

As described above, in one embodiment of the present invention, the FFT output buffers 18 and 19 can hold I / Q symbol data of three consecutive segments,
Then, from the I / Q symbol data of three consecutive segments held in the FFT output buffers 18 and 19,
By outputting I / Q symbol data of a desired one segment and performing detection processing, the desired segment can be selected.

When switching to a segment that is not held in the FFT output buffers 18 and 19, the tuning frequency of the tuner 12 is reset as in the conventional case.

Further, in one embodiment of the present invention, when the user selects the end segment 14 from the state where the user has not selected the segment 13, the frequency shift control circuit 21 controls the operation as shown in FIG. 2G. So segment 1
The tuner 12 has the center frequency f13 of 3 as the tuning frequency.
Is set to. As a result, the tuner 12, the segment 12, the segment 13, and the segment 14 are OFDM.
The signal is output.

Also in this case, in the FFT circuit 17,
Controlled by the frequency shift control circuit 21, a fast Fourier transform corresponding to 3 segments is performed, and as shown in FIG. 2H,
In the FFT circuit 17, the FFT processing is performed on the segment 12, the segment 13 and the segment 14.

Further, the frequency shift control circuit 21
The I / Q symbol data of the segment 14 is output from the FFT output buffers 18 and 19 under the control of FIG.
As shown in, the detection circuit 20 performs detection processing on the I / Q symbol data of the segment 14.

By the way, when the segment 14 at the end is selected from the state where the segment 13 is not selected, FIG.
As shown in, when the center frequency f14 of the segment 14 is set in the tuner 12 as the tuning frequency, the terrestrial digital broadcast signal in the adjacent frequency band is included. In this case, the terrestrial digital signal in the adjacent frequency band is included. If the broadcast signals are in different modes, there is the inconvenience that synchronization cannot be achieved. The processing shown in FIGS. 2G to 2I solves this inconvenience.

Therefore, the user can also select segment 2
Even when the segment 1 at the end is selected from the state in which no channel is selected, the center frequency f2 of the segment 2 is set in the tuner 12 as the tuning frequency, and the segment 1 is set in the FFT output buffers 18 and 19. The I / Q symbol data of the segment 2 and the segment 3 is held, and the I / Q symbol data of the segment 1 is transferred to the detection circuit 20.

As described above, in one embodiment of the present invention, when the user selects an end segment from a state in which the user has not selected a segment adjacent to the end segment,
The tuner 12 is controlled by the frequency shift control circuit 21 so that the center frequency of the segment adjacent to the end segment is used as the tuning frequency, and the I / Q symbol of the end segment is output from the FFT output buffers 18 and 19. FFT output buffers 18 and 19 for outputting data
Are controlled by the frequency shift control circuit 21.

As described above, according to the embodiment of the present invention, a desired segment signal is output from the three segment signals held by the FFT output buffers 18 and 19 and detection processing is performed to output the desired segment signal. The segment of can be selected. That is, the tuner 12 is receiving 3
Within the range of the segment, the segment can be switched without resetting the tuning frequency of the tuner 12. Therefore, within the range of 3 segments received by the tuner 12, switching of segments can be performed in a short time.

[0036]

As described above, according to the present invention, within the range of signals of a plurality of segments received by the tuner, the switching of the segments can be performed without resetting the tuning frequency of the tuner. Therefore, the switching of the segments can be performed in a short time within the range of the plurality of segments received by the tuner.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a main part of an embodiment of the present invention.

FIG. 2 is a diagram for explaining a channel selection method adopted by an embodiment of the present invention.

FIG. 3 is a diagram for explaining an inconvenience that occurs when a center frequency of a segment 14 is set in a tuner as a tuning frequency.

FIG. 4 is a circuit diagram of a main part of an example of a conventional terrestrial digital broadcast receiver.

5 is a diagram for explaining a channel selection system adopted by the conventional terrestrial digital broadcast receiver shown in FIG.

[Explanation of symbols]

1, 11 receiving antenna 2, 12 tuners 3, 13 OFDM demodulator 4, 14 A / D conversion circuit 5, 15 Quadrature demodulation circuit 6, 16 frequency / clock synchronization circuit 7,17 FFT circuit 8, 9, 18, 19 FFT output buffer 10, 20 Detection circuit 21 Frequency shift control circuit

Claims (3)

[Claims] 1. A tuner capable of receiving a plurality of segments, a fast Fourier transform circuit corresponding to the plurality of segments, and a holding circuit for holding a plurality of segment data output from the fast Fourier transform circuit. And terrestrial digital broadcasting receiver. 2. When the end segment is received, the control circuit controls the tuner so that the center frequency of a segment adjacent to the end segment is the tuning frequency. 1. The terrestrial digital broadcast receiver described in 1. 3. A fast Fourier transform circuit corresponding to a plurality of segments, a holding circuit for holding a plurality of segments of data output from the fast Fourier transform circuit, and a control for outputting a desired one segment of data from the holding circuit. An OFDM demodulator having a circuit.